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Initial sites of hepadnavirus integration into host genome in human hepatocytes and in the woodchuck model of hepatitis B-associated hepatocellular carcinoma. Oncogenesis 2017; 6:e317. [PMID: 28414318 PMCID: PMC5520499 DOI: 10.1038/oncsis.2017.22] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 01/11/2017] [Accepted: 03/07/2017] [Indexed: 12/14/2022] Open
Abstract
Hepatitis B virus (HBV) and the closely related woodchuck hepatitis virus (WHV) are potent carcinogens that trigger development of primary hepatocellular carcinoma (HCC). The initial sites of hepadnavirus–host genome integration, their diversity and kinetics of formation can be central to virus persistence and the initiation and progression of HCC. To recognize the nature of the very early virus–host interactions, we explored de novo infection of human hepatocyte-like HepaRG cells with authentic HBV and naive woodchucks with WHV. HepaRG were analyzed from several minutes post exposure to HBV onwards, whereas woodchuck liver biopsies at 1 or 3 h and 6 weeks post infection with WHV. Inverse PCR and clonal sequencing of the amplicons were applied to identify virus–host genomic junctions. HBV and WHV DNA and their replication intermediates became detectable in one hour after virus exposure. Concomitantly, HBV DNA integration into various host genes was detected. Notably, junctions of HBV X gene with retrotransposon sequences, such as LINE1 and LINE2, became prominent shortly after infection. In woodchucks, insertion of WHV X and preS sequences into host genome was evident at 1 and 3 h post infection (h.p.i.), confirming that hepadnavirus under natural conditions integrates into hepatocyte DNA soon after invasion. The HBV and WHV X gene enhancer II/core promotor sequence most often formed initial junctions with host DNA. Moreover, multiple virus–virus DNA fusions appeared from 1 h.p.i. onwards in both infected hepatocytes and woodchuck livers. In summary, HBV DNA integrates almost immediately after infection with a variety of host’s sequences, among which tandemly repeating non-coding DNAs are common. This study revealed that HBV can engage mobile genetic elements from the beginning of infection to induce pro-oncogenic perturbations throughout the host genome. Such swift virus insertion was also evident in natural hepadnaviral infection in woodchucks.
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Locarnini SA, Civitico GM, Newbold JE. Hepatitis B: New Approaches for Antiviral Chemotherapy. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/095632029600700201] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Progress in the development of effective therapeutic regimes for chronic hepatitis B has been slow, mainly due to the lack of promising lead compounds and useful assays for high throughput in-vitro screening. Nucleoside analogue chemotherapy has targeted the inhibition of the hepatitis B virus (HBV) polymerase and achieved inhibition of this unique viral enzyme. The persistence and resistance of HBV covalently closed circular (or supercoiled) DNA, the key replicative intermediate and sole transcriptional template, to existing treatments also poses challenges for the effective development of antiviral chemotherapy. In spite of these difficulties, the process of viral DNA replication, as well as supercoiled DNA generation and processing, is now being elucidated at the molecular level, presenting unique opportunities for new drug targeting and design. This review attempts to highlight these new approaches to the development of treatment regimes for this important disease.
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Affiliation(s)
- S. A. Locarnini
- Victorian Infectious Diseases Reference Laboratory, Fairfield Hospital, Fairfield, Victoria 3078, Australia
| | - G. M. Civitico
- Victorian Infectious Diseases Reference Laboratory, Fairfield Hospital, Fairfield, Victoria 3078, Australia
| | - J. E. Newbold
- Department of Microbiology & Immunology, The School of Medicine, University of North Carolina, Chapel Hill, NC27599–7290, USA
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Lu L, Wang W, Yang C, Kang TS, Leung CH, Ma DL. Iridium(iii) complexes with 1,10-phenanthroline-based N^N ligands as highly selective luminescent G-quadruplex probes and application for switch-on ribonuclease H detection. J Mater Chem B 2016; 4:6791-6796. [DOI: 10.1039/c6tb02316a] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A study was performed to investigate the relationship between molecular structure and G4 sensing ability for a series of iridium(iii) complexes. The complex7was used to construct a G4-based assay for RNase H.
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Affiliation(s)
- Lihua Lu
- College of Chemistry and Pharmaceutical Sciences
- Qingdao Agricultural University
- Qingdao 266109
- China
- Department of Chemistry
| | - Wanhe Wang
- Department of Chemistry
- Hong Kong Baptist University
- Hong Kong
- China
| | - Chao Yang
- State Key Laboratory of Quality Research in Chinese Medicine
- Institute of Chinese Medical Sciences
- University of Macau
- Macao
- China
| | - Tian-Shu Kang
- State Key Laboratory of Quality Research in Chinese Medicine
- Institute of Chinese Medical Sciences
- University of Macau
- Macao
- China
| | - Chung-Hang Leung
- State Key Laboratory of Quality Research in Chinese Medicine
- Institute of Chinese Medical Sciences
- University of Macau
- Macao
- China
| | - Dik-Lung Ma
- Department of Chemistry
- Hong Kong Baptist University
- Hong Kong
- China
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4
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A hybrid chimeric system for versatile and ultra-sensitive RNase detection. Sci Rep 2015; 5:9558. [PMID: 25828752 PMCID: PMC4381352 DOI: 10.1038/srep09558] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 03/11/2015] [Indexed: 12/21/2022] Open
Abstract
We developed a new versatile strategy that allows the detection of several classes of RNases (i.e., targeting ss- or ds-RNA, DNA/RNA hetero-hybrid or junctions) with higher sensitivity than existing assays. Our two-step approach consists of a DNA-RNA-DNA chimeric Hairpin Probe (cHP) conjugated to magnetic microparticles and containing a DNAzyme sequence in its terminal region, and molecular beacons for fluorescence signal generation. In the first step, the digestion of the RNA portion of the cHP sequences in presence of RNases leads to the release of multiple copies of the DNAzyme in solution. Then, after magnetic washing, each DNAzyme molecule elicits the catalytic cleavage of numerous molecular beacons, providing a strong amplification of the overall sensitivity of the assay. We successfully applied our approach to detect very low concentrations of RNase A, E. coli RNase I, and RNase H. Furthermore, we analyzed the effect of two antibiotics (penicillin and streptomycin) on RNase H activity, demonstrating the applicability of our strategy for the screening of inhibitors. Finally, we exploited our system to detect RNase activity directly in crude biological samples (i.e., blood and saliva) and in cell culture medium, highlighting its suitability as cheap and sensitive tool for the detection of RNase levels.
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Block TM, Gish R, Guo H, Mehta A, Cuconati A, Thomas London W, Guo JT. Chronic hepatitis B: what should be the goal for new therapies? Antiviral Res 2013; 98:27-34. [PMID: 23391846 DOI: 10.1016/j.antiviral.2013.01.006] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/14/2013] [Accepted: 01/28/2013] [Indexed: 02/07/2023]
Abstract
Chronic hepatitis B can currently be medically managed with either pegylated interferon-alpha (pegIFN-α) or one of the five nucleos(t)ide analog Direct Acting Antivirals (DAAs) that inhibit the hepatitis B virus (HBV) DNA polymerase. While pegIFN-α is effective in approximately one-third of the treated patients, the polymerase inhibitors significantly reduce viral load in the vast majority of those treated. However, neither pegIFN-α nor nucleosi(t)de analogs are capable of reliably eliminating the virus and achieving a cure. Moreover, the interferons and polymerase inhibitors are recommended by US, European and Asian professional society practice guidelines for use in only a subset of those infected with HBV. This subset is the population with the greatest levels of circulating viral DNA and abnormal liver function. Although this is the population at the highest risk for cirrhosis and liver cancer, those who fall outside the treatment guidelines, with low levels of viral replication and normal serum ALTs, may also benefit from antiviral therapy. The questions are thus: are new classes of drugs needed to manage chronic hepatitis B? Is a cure possible? Is a cure even necessary? It is therefore important to define the meaning of a cure and determine what the goals of new therapies should be. In this article, we address those questions and propose two operational definitions of medically attainable cures. The first is a "functional cure" based on the clinical outcome, in which the patient's life expectancy becomes the same as that of an individual who has resolved his HBV infection without therapy. Because such an outcome cannot be measured over the short term, we also define an "apparent virological cure," based on the stable off-drug suppression of HBV viremia and antigenemia and the normalization of ALTs and other laboratory tests. We suggest that such a virological cure should be the goal of future therapeutics in all patients with chronic hepatitis B. The extent to which a virological cure predicts a functional cure will only be determined by long-term follow-up.
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Affiliation(s)
- Timothy M Block
- Department of Microbiology and Immunology, Drexel University College of Medicine, 3805 Old Easton Road, Doylestown, PA 18902, USA.
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Hasselblatt P, Hockenjos B, Thoma C, Blum HE, Offensperger WB. Translation of stable hepadnaviral mRNA cleavage fragments induced by the action of phosphorothioate-modified antisense oligodeoxynucleotides. Nucleic Acids Res 2005; 33:114-25. [PMID: 15640448 PMCID: PMC546143 DOI: 10.1093/nar/gki155] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Phosphorothioate-modified antisense oligodeoxynucleotides (ASOs) are used to suppress gene expression by inducing RNase H-mediated cleavage with subsequent degradation of the target mRNA. However, previous observations suggest that ASO/RNase H can also result in the generation of stable mRNA cleavage fragments and expression of truncated proteins. Here, we addressed the underlying translational mechanisms in more detail using hepadnavirus-transfected hepatoma cells as a model system of antisense therapy. Generation of stable mRNA cleavage fragments was restricted to the ASO/RNase H pathway and not observed upon cotransfection of isosequential small interfering RNA or RNase H-incompetent oligonucleotides. Furthermore, direct evidence for translation of mRNA fragments was established by polysome analysis. Polysome-associated RNA contained cleavage fragments devoid of a 5′ cap structure indicating that translation was, at least in part, cap-independent. Further analysis of the uncapped cleavage fragments revealed that their 5′ terminus and initiation codon were only separated by a few nucleotides suggesting a 5′ end-dependent mode of translation, whereas internal initiation could be ruled out. However, the efficiency of translation was moderate compared to uncleaved mRNA and amounted to 13–24% depending on the ASO used. These findings provide a rationale for understanding the translation of mRNA fragments generated by ASO/RNase H mechanistically.
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Affiliation(s)
- Peter Hasselblatt
- Department of Medicine II, University of Freiburg Hugstetter Strasse 55, D-79106 Freiburg, Germany.
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Gong Y, Yao E, Tavis JE. Evidence that the RNAseH activity of the duck hepatitis B virus is unable to act on exogenous substrates. BMC Microbiol 2001; 1:12. [PMID: 11504562 PMCID: PMC37354 DOI: 10.1186/1471-2180-1-12] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2001] [Accepted: 07/19/2001] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND The hepadnaviral reverse transcriptase can synthesize DNA on its native RNA template within viral cores but it is usually unable to synthesize DNA employing exogenous nucleic acids as a template. The mechanism of this template commitment is unknown. Here we provide evidence that the RNAseH activity of duck hepatitis B virus reverse transcriptase may also be unable to act on exogenous substrates. RESULTS RNAseH assays were performed under a wide variety of conditions employing substrate RNAs of Duck Hepatitis B Virus sequence annealed to complementary DNA oligonucleotides and permeabilized intracellular viral core particles. Temperature, pH, cation type, salt concentration, substrate concentration, and the sequences of the cleavage sites were varied, and the effects of ATP and dNTPs on RNAseH activity were examined. duck hepatitis B virus RNAseH activity was not detected under any of these conditions, although E. coli or Avian Myeloblastosis Virus RNAseH activity could be detected under all conditions. Access of the RNA substrate to the enzyme within the viral cores was confirmed. CONCLUSIONS These results imply that the RNAseH activity of the DHBV reverse transcriptase may not be able to degrade exogenous RNA:DNA heteroduplexes, although it can degrade heteroduplexes of the same sequence generated during reverse transcription of the endogenous RNA template. Therefore, the RNAseH activity appears to be "substrate committed" in a manner similar to the template commitment observed for the DNA polymerase activity.
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Affiliation(s)
- Yunhao Gong
- Viridae Clinical Sciences, 1134 Burrard St., Vancouver, B.C. V6Z 1Y8, Canada
| | - Ermei Yao
- Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, 1402 South Grand Blvd., St. Louis, MO 63104, USA
| | - John E Tavis
- Department of Molecular Microbiology and Immunology, St. Louis University School of Medicine, 1402 South Grand Blvd., St. Louis, MO 63104, USA
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Abstract
Hepatitis B virus (HBV) is an important etiologic agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Although the mechanism whereby HBV causes HCC is not fully understood, it is likely that there are many relevant molecular pathways that contribute to the development of HBV-associated HCC. This review provides an overview of some of these proposed pathways and their relative importance. It also raises questions on basic and translational research that will signficantly contribute to the better understanding of underlying mechanisms, prevention, and treatment of this tumor type.
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Affiliation(s)
- M A Feitelson
- Department of Pathology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.
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Tencza MG, Newbold JE. Heterogeneous response for a mammalian hepadnavirus infection to acyclovir: Drug-arrested intermediates of minus-strand viral DNA synthesis are enveloped and secreted from infected cells as virion-like particles. J Med Virol 1997. [DOI: 10.1002/(sici)1096-9071(199701)51:1<6::aid-jmv2>3.0.co;2-c] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Wei X, Peterson DL. Expression, purification, and characterization of an active RNase H domain of the hepatitis B viral polymerase. J Biol Chem 1996; 271:32617-22. [PMID: 8955090 DOI: 10.1074/jbc.271.51.32617] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The replication of the hepatitis B viral DNA genome proceeds through a pregenomic RNA intermediate. This pregenomic RNA subsequently serves as the template for the formation of the viral DNA by the reverse transcriptase activity of the viral P gene product. The P gene product is believed to be a multifunctional enzyme with DNA-dependent DNA polymerase, RNA-dependent DNA polymerase, and RNase H activities. Detailed biochemical studies of this protein have not been performed because of the inability to obtain sufficient amounts of the enzyme from the virus and by the inability to produce the enzyme in heterologous expression systems. The RNase H activity is essential for viral replication and is believed to be responsible for the degradation of the RNA pregenomic intermediate as well as for generating the short RNA primer that is required for DNA second strand synthesis. We have assembled an expression vector which directs the synthesis of a protein that corresponds to the putative RNase H domain of the P gene product and having a carboxyl-terminal polyhistidine tag to facilitate purification. The protein has been expressed in Escherichia coli and purified to yield 1-2 mg of protein/liter of culture. This protein has RNase H activity as defined by its ability to degrade the RNA component of RNA-DNA hybrids but not the DNA component. The RNase H has a basic optimum pH, is active only in the presence of reducing agents, and is dependent on the presence of divalent cations, with magnesium being preferred over manganese.
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Affiliation(s)
- X Wei
- Department of Biochemistry and Molecular Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298-0614, USA
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11
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Oberhaus SM, Newbold JE. In situ DNA polymerase and RNase H activity gel assays as applied to hepadnavirus particles. Methods Enzymol 1996; 275:328-47. [PMID: 9026647 DOI: 10.1016/s0076-6879(96)75020-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- S M Oberhaus
- Department of Neurology, University of Colorado Health Sciences Center, Denver 80262, USA
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